Xamarin Android & Websockets

[SSpormann]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I am trying to support websockets with signalR 6 on Android, with a Xamarin app, my code works as intended with longpolling, but there are clear benefits for me in using websockets, and I now have tried for a long time to make this work. But if I set supported transports to Websockets only in the client I get the error message that Longpolling is dissabled in the client, but the server does provide Longpolling,
Unable to connect to the server with any of the available transports. (WebSockets failed: Unable to connect to the remote server) (LongPolling failed: The transport is disabled by the client.)

My client, does look like this;

this._connection = new HubConnectionBuilder()
            .WithUrl($"{_host}/rabbitHub?deviceId={id}", (opts) =>
            {
                opts.HttpMessageHandlerFactory = (x) => new HttpClientHandler
                {
                    ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator,
                };
                opts.AccessTokenProvider = () => Task.FromResult(authToken ?? "bypassauthplz");
                opts.Transports = Microsoft.AspNetCore.Http.Connections.HttpTransportType.WebSockets /*| Microsoft.AspNetCore.Http.Connections.HttpTransportType.ServerSentEvents | Microsoft.AspNetCore.Http.Connections.HttpTransportType.LongPolling*/;
            }  )
            .WithAutomaticReconnect()
            .ConfigureLogging(logging =>
            {
                logging.SetMinimumLevel(LogLevel.Trace);
            }).Build();

and the Server is configured like this:
services.AddSignalR().AddHubOptions<RabbitHub>(options => { options.MaximumParallelInvocationsPerClient = 32; options.KeepAliveInterval = new TimeSpan(0,0,0,5); options.ClientTimeoutInterval = new TimeSpan(0,0,0,10); });

endpoints.MapHub<RabbitHub>("/rabbitHub", options => { options.Transports = HttpTransportType.WebSockets | HttpTransportType.LongPolling | HttpTransportType.ServerSentEvents; });

Expected Behavior

The Expected behavior would be that the client would be aple to connect to the SignalR Server via websockets, this seems to be no Problem with Android, if I connect to an non signalR Websocket I with System.Net.WebSockets, everithing is working as intendet.
So there has to be a bug in the Aspnet.core lib.

I'am using this lib with netstandard 2.1 for the client and .net6 for the server, but changing the server from 5 to 6 did not change anything.

Steps To Reproduce

I would like to provide a simple example, I will provide one as soon as I , find the time to Build one.

Exceptions (if any)

Unable to connect to the server with any of the available transports. (WebSockets failed: Unable to connect to the remote server) (LongPolling failed: The transport is disabled by the client.)

.NET Version

6

Anything else?

No response

[BrennanConroy]

if I connect to an non signalR Websocket I with System.Net.WebSockets, everithing is working as intendet.

SignalR uses System.Net.WebSockets so there shouldn't be any difference in behavior here.

Can you share how are you using System.Net.WebSockets outside of SignalR? Also, capture client and server logs please: https://docs.microsoft.com/aspnet/core/signalr/diagnostics?view=aspnetcore-6.0

Hi @SSpormann. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[SSpormann]

@BrennanConroy
So, if I use Websockets as only transport, I get the above mentioned error,
Unable to connect to the server with any of the available transports. (WebSockets failed: Unable to connect to the remote server) (LongPolling failed: The transport is disabled by the client.)
And no Log on the server side, this seems to me like signalr is preventing the use of websockets by it self.

If I allow longpolling I get,
[Authorization, Bearer sometoken] [Host, myhost] [User-Agent, Microsoft SignalR/6.0 (6.0.3+c911002ab43b7b989ed67090f2a48d9073d5118d; Linux; .NET; Mono 6.12.0 (2020-02/adf1bc4335d))] [x-requested-with, XMLHttpRequest] [x-forwarded-proto, https] 2022-05-27 08:04:48.4049||DEBUG|AuthService.AuthenticationHandlers.EpasAuthenticationHandler|Bypassing auth for /myHub: /myHub 2022-05-27 08:04:48.4049|8|DEBUG|AuthService.AuthenticationHandlers.EpasAuthenticationHandler|AuthenticationScheme: EpasAuth was successfully authenticated. 2022-05-27 08:04:48.4094|4|DEBUG|Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionDispatcher|Establishing new connection. 2022-05-27 08:04:48.4094|5|DEBUG|Microsoft.AspNetCore.SignalR.HubConnectionHandler|OnConnectedAsync started.

And the connection is working, from here on.

I used this example to validate that the concept should in theory work,

https://devblogs.microsoft.com/xamarin/developing-real-time-communication-apps-with-websocket/

(You will have to Update some/all nuget packages to make it work)

Maybe it has something to do with teh setup of my project, the client is currently in a netstandard 2.1 project that I referenced in my project, beacause we are using the same client on multiple platforms.

If I use the same client under WPF, with only transport Websocket, every thing works fine.

[SSpormann]

I can now provide a sample that shows a working version with playn websockets, and a version that is working with signalr Longpolling enabled and is not working with signalr only using websockets on the client side.

You can finde the project here:

If you prefere an other methode to recieve the sample please, contact me we can figure something out.

To use the sample there is a solution under the folder easychat, there should be two Xamarin projects inside, one is called MyEasyChat, this is using plain websockets, combine this project with the server in the folder myeasychat und you can see that the concept of using websockets with System.Net.WebSockets does work. If you now want to try the faulty projekt, you have to use the project SignalRMyEasyChat under the EasyChat.sln and combine this with the myeasychat-signalr server under the folder with tehe same name(myeasychat-signalr) this, should currently promt the same error as I provided earlier.

Unable to connect to the server with any of the available transports. (WebSockets failed: Unable to connect to the remote server) (LongPolling failed: The transport is disabled by the client.)

if you now change the line of code in the EasyChat.sln -> SignalRMyEasyChat -> ChatPageViewModel line: 41

From:
opts.Transports = Microsoft.AspNetCore.Http.Connections.HttpTransportType.WebSockets /*| Microsoft.AspNetCore.Http.Connections.HttpTransportType.ServerSentEvents | Microsoft.AspNetCore.Http.Connections.HttpTransportType.LongPolling*/;

To:
opts.Transports = Microsoft.AspNetCore.Http.Connections.HttpTransportType.WebSockets | Microsoft.AspNetCore.Http.Connections.HttpTransportType.ServerSentEvents | Microsoft.AspNetCore.Http.Connections.HttpTransportType.LongPolling;

you should see that Signal-R is indeed working, but it does not work with websockets as transport.

you will have to change the IP-Adresses, in the ChatPageViewModel files, to your Server-IP.

I would investigate this problem further by my self but, currently I have no Idea how to setup the aspnet core repository in a way, that I would be able to debug this problem, I tried to setup a debug environment a year ago and stoped trying after 2 days. If someone has a guide on how to debug the aspnet.core project that would help me out a great deal.

I allso tryed to capture network traffic, from the phone to the server and as I suspected earlier, there is not even a connection request exiting the device, so I belive ther must be a logic error that throws the exception client side.

[BrennanConroy]

Please provide the repro app as a github repository.

[SSpormann]

@BrennanConroy here you go.

[davidfowl]

@SSpormann is it private? It says not found.

[SSpormann]

@BrennanConroy sorry should be public now

[davidfowl]

Unrelated: https://github.com/SSpormann/EasyChat-SignalR/blob/afb56ae1a2b5c00a2d8d4f445688c7f6a3012772/myeasychat-signalr/myeasychat-signalr/Program.cs#L15

Why would you allow the client to send a message of 1GB? That's a potential security issue.

[davidfowl]

Also unrelated, sent a clean up PR SSpormann/EasyChat-SignalR#1

[davidfowl]

@SSpormann can you remove specifying all of the transports from both the client and server?